000
AGNT40 KWNM 091423
MIMATN
Marine Weather Discussion for N Atlantic Ocean
NWS Ocean Prediction Center Washington DC
923 AM EST FRI DEC 9 2016
.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Atlantic Ocean W of 50W from 30N to 50N.
At 12z a cold front was across the far northeast portions of the
NT2 waters with a high pres ridge over the rest of the NT2 waters
and NT1 waters. Will allow current forecast to continue as is in
this intermediate update as see no reason for wholesale major
tweaks given 06z GFS/NAM are in good agreement with the prior 00z
model cycle.
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PREVIOUS DISCUSSION...
Over the short term...In the wake of an arctic cold front passing
SE of the NT2 waters...the new 00Z models remain consistent in
forecasting strong high pressure to build in from the W today into
tonight while a series of surface trofs pass SE across the Nrn
waters maintaining a strong WNW gradient with at times marginal
gale force winds. Based on the latest surface observations and
earlier ASCAT scatterometer passes...likely due to the strong cold
air advection and impressive negative static stability...none of
the 00Z models have initialized this gradient strong enough.
Therefore will populate our forecast wind grids with the stronger
00Z GFS first sigma level winds for early today...boosted up 5-10
percent on average. Then late today through Saturday night...with
the consensus of the 00Z models providing support...will continue
to use the previously populated official wind grids which were
based on the 08/00Z GFS first sigma level winds. So will be make
some minor short term changes to the previously forecasted gale
warnings in the strong WNW gradient today/tonight.
In the long range...Versus its previous 18Z run...the 00Z GFS has
trended less amplified with its forecasted upper level pattern by
late Monday into Tuesday and as a result now forecasts a weaker
surface low to pass just N of the area Monday night while pulling
a strong cold front offshore. Though weaker...this 00Z GFS
solution is still the strongest of the 00Z global models and has
the most widespread associated gale force boundary layer winds.
Overall the 00Z GEFS Mean supports the 00Z GFS solution. The 00Z
global model that is closest to the 00Z GFS is the slightly weaker
00Z GEM. The 00Z UKMET shares similar forecast timing with the 00Z
GFS but is significantly weaker. Versus its previous 12Z run...the
00Z ECMWF has trended towards a more amplified solution and is now
more similar to the 00Z GFS solution. Therefore with the 00Z
GFS/ECMWF now converging towards similar solutions and being
supported by the 00Z GEFS Mean...as a compromise will populate our
wind grids on Sunday through Monday night with a 50/50 blend of
the 00Z ECMWF boundary layer winds and the 00Z GFS first sigma/10m
winds (using our smart tool that places 00Z GFS first sigma layer
winds in unstable areas and 00Z GFS 10m winds in stable areas). So
as a result of these blended winds...will expand the area of
previously forecasted possible gale warnings Monday/Monday night
to now include the SE NT1 waters.
Then further out in the long range...Tuesday/Tuesday night...the
disparity between the 00Z global models becomes enormous. For now
with very low forecast confidence...to be in some agreement with
the latest WPC medium range guidance...will continue with the same
50/50 blend of the 00Z GFS/ECMWF boundary layer winds on
Tuesday...then will transition to all 00Z GFS first sigma/10m
boundary layer winds on Tuesday night.
.SEAS...The higher 00Z ECMWF WAM has initialized better than the
00Z Wavewatch III. Therefore will populate our forecast wave
grids with the 00Z ECMWF WAM for today through Saturday night.
Then since a blended 00Z GFS/ECMWF solution will be used...will
populate with a 50/50 blend of the 00Z Wavewatch III and 00Z ECMWF
WAM for Sunday through Tuesday...followed by all 00Z Wavewatch III
seas on Tuesday night.
.EXTRATROPICAL STORM SURGE GUIDANCE...Similar to its previous
respective runs...the 00Z ESTOFS continues to forecast a slightly
more significant negative surge in the strong WNW gradient along
the coast from Long Island Sound to Delaware Bay today into early
Saturday than forecast by the 00Z ETSS model. The ESTOFS is likely
overdoing this surge and would instead favor a compromise between
the two models.
.WARNINGS...Preliminary.
.NT1 New England Waters...
.ANZ800...Gulf of Maine...
Gale today into tonight.
.ANZ805...Georges Bank west of 68W...
Gale today into tonight.
Gale Possible Monday.
.ANZ900...Georges Bank east of 68W...
Gale today into tonight.
Gale Possible Monday.
.ANZ810...South of New England...
Gale today into tonight.
Gale Possible Monday.
.ANZ815...South of Long Island...
Gale today into tonight.
Gale Possible Monday.
.NT2 Mid-Atlantic Waters...
.ANZ820...Hudson Canyon to Baltimore Canyon...
Gale today into tonight.
.ANZ915...Hudson Canyon to the Great South Channel...
Gale today into tonight.
Gale Possible Monday into Monday night.
.ANZ920...Baltimore Canyon to the Great South Channel...
Gale today into tonight.
Gale Possible Monday into Monday night.
.ANZ905...The Great South Channel to the Hague Line...
Gale today into Saturday night.
Gale Possible Monday into Monday night.
.ANZ910...East of the Great South Channel and south of 39N...
Gale today into tonight.
Gale Possible Monday into Monday night.
.ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon...
Gale Possible Monday into Monday night.
$$
.Forecaster Holley/Vukits. Ocean Prediction Center.